Thermal Barrier Coatings for Diesel Engine Components

An additional set of problems will be associated with the transfer of aerospace TBCs to diesel engines. This is partly because thicker coatings will be required to meet the insulation needs for most of the more advanced applications, and higher stresses are generally associated with thicker coatings. Currently NASA-Lewis is managing two DOE-sponsored contracts which are designed to develop thermal barrier coatings for truck diesel engines. (This program has been discussed at this conference). This work is building, in part, on earlier programs which led to the development of the thick plasma sprayed turbine blade tip-clearance seals which are now flying in certain commercial gas turbine engines (ref.24). These seals, like coatings for diesel engine piston heads and valves, operate at temperatures too low for bond coat oxidation to be a concern. As a result, it possible to use intermediate layers of mixed,ceramic and metal to ; alleviate thermal expansion mismatch strains. Possibly,the most important difference between the environment encountered by coated diesel engine components versus the environment encountered by the seals in a turbine engine involves the discontinuous combustion in a piston engine. It is believed that the repeated temperature and pressure spikes associated with combustion in a diesel engine may fatigue the coating system. In fact, recent results have shown that plasma sprayed zirconia-yttria experiences fatigue failure as illustrated in figure 3 from reference 19.

The solar Stirling engine is progressively becoming a viable alternative to solar panels for its higher efficiency. Stirling engines might be the best way to harvest the power provided by the sun. This is an easy-to-understand explanation of how Stirling engines work, the different types, and why they are more efficient than steam engines.